A wire connecting device for connecting a fiber-core conductor configured by stranding a plurality of fiber-core conductive wires. The wire connecting device includes a vis having a rod-shape pin and a head extending outwardly from the pin. A plate-shape terminal connects with the vis by inserting the pin in an opening. The head matches up with an overlap portion of the terminal so that the fiber-core conductor is clamped between the head and the overlap portion of the terminal connect electrically the fiber-core conductor and the terminal. The conductor passes over and contacts an end portion of the pin. The pin and the inner surface of the opening are curved surfaces to eliminate sharp corners.